Knotter system for a baler

ABSTRACT

A knotter system for a baler, including a needle; a tucker arm; a billhook; and a driver adapted to make the billhook perform at least a first full rotation during the first knot forming cycle and a second full rotation during the second knot forming cycle. The driver comprises a pinion and at least a first and second gear stretch provided along a circumference of a disc. The disc is provided with a recess downstream of at least one of the first gear stretch and the second gear stretch. An obstacle is arranged for engaging the pinion when moving in the recess. The recess and obstacle are configured to rotate the pinion over a determined angle and back to move the upper lip of the billhook away from the lower lip and back after at least one of the first full rotation and the second full rotation.

FIELD OF THE INVENTION

The present invention relates to a knotter system, and in particular toa knotter system for a baler for forming two consecutive knots during asingle knotter cycle, said knotter cycle comprising at least a firstknot forming cycle and a second knot forming cycle.

BACKGROUND OF THE INVENTION

Rectangular bales are able to maintain their shape by means of a seriesof parallel extending twine loops, provided lengthwise around the bales.Known balers typically use automatic knotters by which two knots aremade on every loop for binding a bale. An example of such a knottersystem for a baler is disclosed in U.S. 2006/0012176 in the name of theApplicant, the disclosure of which is included herein by reference. Theknotter system disclosed in U.S. 2006/0012176 has the advantage that twoconsecutive knots can be formed during one operation cycle, without theformation of twine tails.

Similar improved knotter systems are disclosed in patent applications inthe name of the Applicant with publications numbers WO2015/014616,WO2014/060245 and U.S. 2015/0272011, the disclosure of which is includedherein by reference.

In prior art knotter systems, it is typically desirable that the secondknot is a loop knot. Also, it may be desirable that the first knot is aloop knot. To achieve good loop knots the settings are very critical.Also the twine type and quality is critical to achieve a good result.

SUMMARY OF THE INVENTION

The object of embodiments of the present invention is to further improvethe knotter system of U.S. 2006/0012176 and WO2014/060245, and more inparticular to improve the forming of the first and/or second knot suchthat a loop knot can be achieved in a less critical way. More inparticular, an object of embodiments of the invention is to obtain alsoa good first and/or second loop knot with non-optimal settings and/orwith twine having a reduced quality.

According to a first aspect there is provided a knotter system forperforming a knotter cycle of a baler, comprising at least a first knotforming cycle and a second knot forming cycle. The knotter systemcomprises: a needle configured for delivering a needle twine; a tuckerarm configured for delivering a tucker twine; a billhook assembly; and adrive means. The billhook assembly comprises a billhook with a lower lipand an upper lip mounted pivotally with respect to lower lip. Thebillhook is mounted rotatably around a rotation axis, preferably aninclined rotation axis.

The drive means is adapted to make the billhook perform at least a firstfull rotation around its rotation axis during the first knot formingcycle and a second full rotation around its rotation axis during thesecond knot forming cycle. The drive means comprise a pinion and atleast a first and second gear stretch provided along the circumferenceof a disc. The pinion is adapted to cooperate with the first and secondgear stretch for making the billhook perform the first and second fullrotation respectively when said disc is rotated, for forming the firstand the second knot, respectively. The disc is provided with a recessdownstream of at least one of said first gear stretch and said secondgear stretch. An obstacle is arranged for engaging the pinion whenmoving in the recess. The recess and obstacle are configured to rotatesaid pinion over a determined angle and back in order to move the upperlip of the billhook away from the lower lip and back after at least oneof said first full rotation and said second full rotation.

By rotating the pinion over a determined angle and back in order to movethe upper lip of the billhook away from the lower lip and back after thefirst full rotation and/or after the second full rotation, the formingof a first and/or second loop knot is improved. Indeed, by brieflyopening the billhook after the first full rotation and/or after thesecond full rotation, a first and/or second loop knot can be formed andthe first and/or second loop knot is released from the billhook in amore secure manner. In that manner the knotter settings are lesscritical and the twine type and quality is less critical. In addition,the recess in the knotter disc and the obstacle are simple and robustfeatures which can be easily added in existing knotter systems.

Preferably, the obstacle is a spring mounted element fixed to the disc.More preferably the obstacle is any one of the following: aspring-mounted arm, a spring mounted wheel. Such a spring-mountedobstacle is simple and robust and allows the pinion to be accuratelypressed/rotated into the recess and returned/counter-rotated whenreleased.

Preferably, the recess extends along the circumference of the disc overan angular distance of 10-90 degrees, preferably 20-60 degrees, morepreferably between 30 and 50 degrees. In that manner a brief opening ofthe billhook is obtained which does not hinder the other movingcomponents during the knotter cycle.

In an exemplary embodiment, at least one of the first gear stretch andthe second gear stretch has an outer gear stretch arranged on anoutwardly protruding portion of the disc, and an inner gear stretchdelimited by a downstream and upstream bottom land portion; and thepinion comprises an outer teeth range configured to cooperate with theouter gear stretch, and an inner teeth range configured to cooperatewith the inner gear stretch, said inner teeth range being delimited by acontact portion configured to rotate in said downstream and upstreambottom land portion and to slide over the disc when the pinion is notengaged with the first or second gear stretch. Such an embodiment allowsfor a good control of the rotation of the billhook during the first andsecond knot forming cycle.

In an exemplary embodiment the recess is configured to receive thecontact portion and to cause the contact portion to rotate over thedetermined angle and back. The contact portion may have a slightlycurved contact surface.

Preferably, the recess, the inner gear stretch and the downstream andupstream bottom land portions are positioned on the same ring-shapedpath around an axis of the disc.

Preferably, the angular distance between the recess and the downstreambottom land portion is smaller than 30 degrees, preferably smaller than20 degrees. In that manner the additional opening of the billhookimmediately follows the first and/or second full rotation of thebillhook, and does not significantly impact the knotter cycle.

Preferably the obstacle is configured to engage the outer teeth range ofthe pinion, such that the pinion is rotated into the recess. This outerteeth range protrudes out of the recess and can be easily engaged by theobstacle.

Preferably the recess, seen in a downstream direction, slopes firstgradually downwardly and next gradually upwardly. In that manner thepinion can rotate gradually in the normal rotation direction and then ina counter-rotation direction, while passing over the recess.

In an exemplary embodiment the billhook assembly is configured toposition the upper lip away from the lower lip in a first angular rangeand to position the upper lip away from the lower lip in a secondangular range of at least one of the first and second full rotation,wherein the first angular range is located within a range between 0° and160°, and the second angular range is located within a range between160° and 360°, wherein 0° corresponds with a start position of thebillhook assembly. By positioning the upper lip away from the lower lipin the first angular range, i.e. by opening the billhook after thetwines have been draped over the billhook, the twines can be movedbackwards on the billhook in the direction of the pivot point betweenthe lower lip and the upper lip, thus ensuring that the twines areproperly positioned on the billhook. In the second angular range theopen billhook allows to perform the knotting, wherein twines arepositioned between the lower lip and the upper lip as in prior artsolutions. The opening of the billhook in the first angular range can bedone both in the first knot forming cycle and in the second knot formingcycle.

In an exemplary embodiment the billhook assembly is configured to movethe upper lip away from the lower lip and back a first time in the firstangular range and to move the upper lip away from the lower lip a secondtime in the second angular range. Such an embodiment has the advantagethat the billhook may be briefly opened during the first angular rangeand then closed again, in order not to hinder the movement of othercomponents, such as the swing arm, see further, during a knot formingcycle.

In another exemplary embodiment the billhook assembly is configured tomove the upper lip away from the lower lip in the first angular rangeand to move the upper lip back to the lower lip in the second angularrange. In other words, in such an embodiment the billhook is opened inthe first angular range and remains open until the end of the firstangular range. In such an embodiment, the billhook may e.g. be opened alittle in the first angular range and then opened more in the secondangular range.

In an exemplary embodiment the first angular range is located within arange between 0° and 130°, preferably within a range between 0° and 90°.By performing the first opening of the billhook at the beginning of therotation, the twines can be positioned properly right at the beginning.

In an exemplary embodiment the billhook assembly comprises a camsurface, and the billhook is provided with a cam follower in contactwith the cam surface. The cam surface may be provided with a first and asecond cam configured for pushing the upper lip away from the lower lip,in the first angular range and in the second angular range,respectively, during said first full rotation and during said secondfull rotation. In another embodiment the cam surface may be providedwith a single cam causing the billhook to open in the first angularrange and to remain open in the second angular range. Embodiments with acam surface and cam follower have the advantage that the opening of thebillhook is well controlled and predictable. However, it is alsopossible to give an upper lip of the billhook a suitable shape andweight such that it is opened automatically during the first angularrange. More in particular the upper lip may be provided with a hook-likeend part protruding in the direction of the lower lip. The hook-like endpart has an inner face making an obtuse angle α with a lower face of anelongate portion of the upper lip. By increasing the angle the billhookcan be more easily opened by a strand. When such an embodiment is usedan appropriate compromise has to be found between the shape of the upperlip, and in particular of the hook-like end part, and the tension instrands. In an exemplary embodiment the billhook assembly is configuredto position the upper lip away from the lower lip in the first angularrange of the first full rotation and to position the upper lip away fromthe lower lip in the second angular range of the first full rotation,and to position the upper lip away from the lower lip in the firstangular range of the second full rotation and to position the upper lipaway from the lower lip in the second angular range of the second fullrotation. In other words, it is preferred to do the opening of thebillhook in the first angular range, both during the first knot formingcycle and during the second knot forming cycle. When a cam surface andupper lip with cam follower is used, it is clear that this it isdesirable to use the same cam surface for the first and the second knotforming cycle, so that the opening/closing cycle of the billhook is thesame during the first and the second knot forming cycle.

In an exemplary embodiment the knotter system further comprises a twinereceiver and a swing arm. The twine receiver may be configured forholding the needle twine and the tucker twine. The swing arm may beadapted for cutting twines between the billhook and the twine receiver.The drive means may then be further configured to move the swing arm afirst time from a rest position to an extended position and back duringthe first knot forming cycle and a second time during the second knotforming cycle. In an exemplary embodiment the drive means comprise a camtrack and a cam follower, said cam follower being connected with theswing arm, and said cam track being provided in said disc or in a membermounted for rotating synchronously with said disc, and being adapted formoving the swing arm a first time and a second time during the first andthe second knot forming cycle, respectively.

In an exemplary embodiment the knotter system further comprises a twinefinger. The twine finger may be configured for guiding at least theneedle twine, said twine finger being mounted moveably below thebillhook and the swing arm. The drive means may then be furtherconfigured to move the twine finger at least a first time during thefirst knot forming cycle and a second time during the second knotforming cycle.

Preferably the swing arm is configured for sweeping a formed knot fromthe billhook during the first knot forming cycle and during the secondknot forming cycle, respectively.

Preferably the twine receiver is adapted to let the twines slip duringthe second knot forming cycle so that cutting of the needle and tuckertwine is avoided when forming the second knot. By allowing the twines toslip during the second full rotation of the billhook, the cutting of thetwines is avoided.

According to an exemplary embodiment, the twine receiver comprises atwine disc and a twine holder. The twine holder is adapted to clamptwines against the twine disc. The knotter system may further comprisesecond drive means adapted for rotating the twine disc during a firstturn whilst clamping twines for forming the first knot, and for rotatingthe twine disc during a second turn whilst letting twines slip for theforming of the second knot. According to an exemplary embodiment, thetwine disc is provided with at least a first and a second notch forreceiving the twines. The twines are typically in the first notch duringthe first turn and in the second notch during the second turn. Notehowever that during the beginning of the second turn, end parts of thetwines may still be in the first notch. However, during the forming ofthe second knot, the end parts will slip first out of the first notchand then out of the second notch. According to a possible embodiment,the second notch is shaped in such a way that the twines are allowed toslip out of the second notch during forming of the second knot.According to another possible embodiment, the twine receiver is providedwith biasing means for setting a bias for the clamping action by thetwine holder. The biasing means may then be adapted to set a first biasduring the first turn, and a second bias during the second turn. Thefirst bias is chosen such that the twines are firmly clamped, while thesecond bias is chosen such that the twines are allowed to slip out ofthe twine receiver.

According to a preferred embodiment, the swing arm is provided with acutter and a removal means. The cutter is adapted for cutting twinesbetween the billhook and the twine receiver, whilst moving from the restposition to the extended position, and the removal means are adapted forsweeping twines from the billhook whilst moving from the rest positionto the extended position. Typically, the removal means have a shapewhich is complementary to the shape of the billhook in order tofacilitate the removal of the twines.

According to another aspect of the invention there is provided a balercomprising a plurality of knotter systems according to any one of theembodiments defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of this invention will be apparent upon consideration ofthe following detailed disclosure of exemplary non-limiting embodimentsof the invention, especially when taken in conjunction with theaccompanying drawings wherein:

FIG. 1 is a fragmentary, side elevational view of a baler having adouble knotter tying mechanism;

FIG. 1A is a detailed view of a needle end portion;

FIG. 2 is a diagrammatic view of a complete and a partial double-knottedloop without the forming of twine tails;

FIGS. 3A-3D are exploded perspective views of an exemplary embodiment ofa double knotter system of the invention, looking from different angles;

FIG. 3E is a top view of an exemplary embodiment of a knotter disc of adouble knotter system of the invention;

FIG. 3F is a perspective view of a pinion for use in the exemplaryembodiments of FIGS. 3A-3E;

FIG. 4A, is a perspective view of a billhook assembly according to anembodiment;

FIG. 4B is a schematic bottom view of the cam surface of the billhookassembly of FIG. 4A.

FIG. 5 is a perspective view of an exemplary embodiment of a billhook;

FIGS. 6A to 6J are fragmentary, schematic views illustrating thesuccessive steps of a first knot forming cycle of a double-knottingoperation.

FIG. 7A is a perspective view of a first exemplary embodiment of a twinereceiver;

FIG. 7B is a perspective view of a second exemplary embodiment of atwine receiver; and

FIG. 8 is a schematic view of a modified upper lip of a billhookaccording to an exemplary embodiment.

FIGS. 9A to 9I are fragmentary, schematic views illustrating thesuccessive steps of a second knot forming cycle of a double-knottingoperation.

DESCRIPTION OF THE DRAWING

In the description which follows and in certain passages already setforth, the principles of the present invention will be described interms of “twine” and “knots” formed in such twine. However, it is to berecognized that such principles extend to wire and twisted junctions ofwire as well as twine and knots.

Many of the fastening, and connection processes, and other means andcomponents utilized in this invention are widely known and used in thefield of the invention described, and their exact nature or type is notnecessary for an understanding and use of the invention by a personskilled in the art, and therefore they will not be discussed insignificant detail. Also, any reference herein to the terms “left” or“right” are used as a matter of mere convenience, and are determined bystanding at the rear of the machine facing in its normal direction oftravel.

The baler 1 illustrated in FIG. 1 has a rectangular bale case 2 that issupported by ground wheels 3. The bale case 2 defines a bale chamberwherein material is pushed in through a curved duct 4. A plunger 5reciprocates within the bale case to intermittently pack fresh chargesof material from the duct 4 rearward in the chamber in the direction ofthe arrow 6. When the bale reaches a predetermined size, a trigger 7 ispulled by a rod 8. This rod 8 engages a dog clutch 9, the clutch 9 inturn being connected to a tying mechanism 10 and a set of needles 11. Aswill be appreciated, the tying mechanism comprises a set of individualknotters 10 provided crosswise on top of the bale chamber at intervals.Each knotter 10 has an associated needle 11 for assisting in forming anindividual loop around a finished bale. When the bale needs tying, thedog clutch 9 connects the knotters 10 and their needles 11 via a drivechain 12 to a source of driving power to initiate the tying operation.As the individual knotters 10 all operate in an identical manner, itsuffices to describe the present invention in relation to only one suchknotter 10.

The needle 11 is swingably mounted on the bale case 2 by a pivot 13 andis swung back and forth across the bale chamber by a linkage 14, whichis activated by the clutch 9. The needle 11 has an “at-home” or restposition fully below the bale case 2 as illustrated in FIG. 1 and a“full-throw” position extending completely across the bale case 2 asillustrated, for example, in FIG. 6C. As illustrated in FIG. 1A, the tip20 of needle 11 has an eyelet 21 defined therein by the opposedfurcations 22 and 23 of the bifurcated tip 20 in conjunction with a pairof longitudinally spaced, transversely extending rollers 24 and 25.

With reference to FIG. 2, to the left of loop 62 is a partial loop 62 awhich is in the process of being formed. The already completed bale onthe right is wrapped by a loop 62 formed by a top and bottom twine 64,66 which are knotted in the two top corners of the bale, see knots 68and 77. The partial loop 62 a around the bale that is being formedcomprises a top twine 64 a (also called tucker twine) and a bottom twine66 a (also called needle twine). The top twine 64 a emanates from asource of twine supply 72, while the bottom twine 66 a emanates from anentirely separate, second source of twine supply 74. At the particularpoint in the sequence chosen for illustration, a knot 68 a (this is thesecond knot of an already executed knotter cycle where knot 70 wasformed as the first knot and knot 68 a as the second knot) is inexistence, and the bale is approaching that length where the needle 42is ready to swing into operation and present the twines 64 a and 66 a tothe knotter 40 to start a knotter cycle in which two consecutive knotsare being formed. In a finished bale, the loop 62 is made from twostrands of binding material, i.e., one strand of twine 64 along the topside of the bale and a second strand of twine 66 along the bottom sideof the bale and its two opposite, vertical ends. The strands of twine 64and 66 together form the continuous loop 62. Together, they fullycircumscribe the bale. The knot 70 (this is the first knot of a knottercycle) is typically a traditional knot. The knot 68, 68 a of a bale(this is the second knot of a knotter cycle) may be a traditional knotor a so called loop-knot. In a loop-knot the ends of the twines 64, 64 aand 66, 66 a of the knot 68, 68 a are released from a retained positionso they can be pulled back as will be described further to form a smallloop on top of the knot. The knot 68, 68 a itself holds the ends of thetwines 64, 64 a and 66, 66 a united with the knot 68, 68 a.

The knotter is similar in many respects to the knotters disclosed inUS2006/0012176, WO2015/014616 and WO2014/060245 in the name of theApplicant, and the disclosure of those documents is herein incorporatedby reference.

With this short explanation in mind, the details of the embodimentsaccording to the present invention will now be described. FIGS. 3A-Dillustrate a first embodiment of a knotter 10 according to theinvention. For convenience the same reference numerals have been usedfor referring to similar elements in the different embodiments.

The knotter 10 of FIGS. 3A-D comprises a generally circular element,also called knotter disc 501 that is secured to a drive shaft 502 forrotation with the latter through one full revolution when the clutch 9is engaged. The shaft 502 is typically supported by a forwardly inclinedframe 15 (see FIG. 1) attached to the top of the bale case 2, and theframe 15 also supports the knotter components for forming the knots inresponse to rotation of the knotter disc 501.

The knotter components include a rotary billhook 100, supported by theframe 15 for rotation about an inclined axis 106 (see FIG. 5); a twinedisc 201 rearward of and adjacent to the billhook 100 for holding topand bottom twines 64 a and 66 a in position for engagement by thebillhook 100 during rotation of the latter; and a swing arm 400pivotally attached to the frame 15 by a bolt 420. The top and bottomtwines 64 a and 66 a are held in notches 211, 212 in the rotating twinedisc 201 by a retainer or twine holder 202, see FIG. 3D. The tensioningforce of this retainer 202 to the twine disc 201 can be adjustedmanually by changing the tension of a leaf-spring 220 when a bolt isloosened or tightened.

The billhook assembly is illustrated in detail in FIG. 4A and comprisesa billhook 100 and a cam surface 110. The billhook 100 is shown indetail in FIG. 5 and comprises a lower lip 102, and an upper lip 101connected around a pivot point with the lower lip 102. During a tyingcycle, the billhook 100 performs at least a first full rotation aroundits rotation axis 106 during a first knot forming cycle and a secondfull rotation around its rotation axis 106 during a second knot formingcycle. When the billhook 100 rotates around its axis 106, a cam follower103, which is connected to the upper lip 101, engages a cam surface 110having a first cam 111 and a second cam 112. When rotating over thefirst cam 111 or over the second cam 112, the cam follower 103 will pushthe upper lip 101 away from the lower lip 102. As will be explained indetail below, during the first knot forming cycle, the first cam 111will cause a first opening of billhook 100 (i.e. the upper lip 101moving away from the lower lip 102) to ensure a good positioning of thetwines 64 a and 66 a on the billhook 100, see FIG. 6E, and the secondcam 112 will cause a second opening of billhook 100 enabling the twines64 a and 66 a to enter in between the two lips 101 and 102 while thebillhook 100 is rotated. In other words, the billhook assembly isconfigured to position the upper lip 101 away from the lower lip 102 ina first angular range 121 of the first full rotation and to position theupper lip 101 away from the lower lip 102 in a second angular range 122of the first full rotation. Similarly, as will be explained in detailbelow, during the second knot forming cycle, the first cam 111 willcause a first opening of billhook 100 to ensure a good positioning ofthe twines 64 b and 66 b on the billhook 100, see FIG. 9C, and thesecond cam 112 will cause a second opening of billhook 100 enabling thetwines 64 b and 66 b to enter in between the two lips 101 and 102, seeFIG. 9E. In other words, the billhook assembly is configured to positionthe upper lip 101 away from the lower lip 102 in a first angular range121 of the second full rotation and to position the upper lip 101 awayfrom the lower lip 102 in a second angular range 122 of the second fullrotation. Since the same cam surface with the first and second cam 111,112 is used for the first and second full rotation of billhook 100, thefirst and second angular ranges 121, 122 are also the same for the firstand second full rotation. The first angular range 121 is located withina range between 0° and 160°, and the second angular range 122 is locatedwithin a range between 160° and 360°. Preferably, the first angularrange is located within a range between 0° and 130°, more preferablywithin a range between 0° and 90°.

The first and second angular range are schematically illustrated in FIG.4B. Reference B indicates a start position for the cam follower 103, andarrow R indicates the rotational direction of the billhook 100. In thestart position B the cam follower 103 may be positioned between thesecond cam 112 and the first cam 111 (FIG. 4B). Alternatively, in thestart position B, the cam follower 103 may be positioned at thebeginning of the first cam 111, i.e. in a position in which the billhook100 is open (FIG. 4B). When the first rotation starts, the billhook 100is opened a first time in the first angular range 121 of the firstrotation when the cam follower 103 passes over the first cam 111. Nextthe billhook is closed again as the cam follower leaves the first cam111. When the cam follower 103 enters the second angular range 122, thebillhook 100 is opened a second time when it reaches the first end ofthe second cam 112. The same sequence is followed for the second fullrotation.

In the illustrated embodiment two cams 111, 112 are provided such thatthe upper lip 101 is moved away from the lower lip 102 and back a firsttime in the first angular range and moved away from the lower lip 102and back a second time in the second angular range. However, in otherembodiments there could be provided one long cam extending from thefirst angular range 121 to the second angular range 122, such that thebillhook 100 remains open, and does not close fully between the tworanges. In other words, the billhook assembly is configured to move theupper lip 101 away from the lower lip 102 in the first angular range andto move the upper lip 101 back to the lower lip 102 in the secondangular range. For example, the cam may be adapted such that in thefirst angular range the billhook 100 opens only a little whilst openingfully in the second angular range.

The length l of the lower lip 102 measured from the pivot point ispreferably larger than 35 mm, in order to ensure that the twines can beproperly placed on the billhook 100 and do not slide off the billhook100. The upper lip 101 is provided at a free end thereof with adownwardly protruding end part 104, and the lower lip 102 is providedwith an end recess 105 for receiving said protruding end part. In thatway the upper lip 101 can be placed against or very close to the lowerlip 102 ensuring an improved stripping of the knot formed on thebillhook 100.

The foregoing described movement on the part of the billhook 100 and thetwine disc 201 are brought about by operable inter-engagement of thegear stretches 504, 505 and gear sections 605, 606, 606′, 606″ on theknotter disc 501 with their respective gears 503 and 604 on the billhook100 and the twine disc 201.

Now the drive means adapted to make the billhook 100 perform at least afirst full rotation around its rotation axis 106 during the first knotforming cycle and a second full rotation around its rotation axis 106during the second knot forming cycle will be described in more detail.The drive means comprise a pinion 503 and at least a first and secondgear stretch 504, 505 provided along the circumference of the knotterdisc 501, see FIG. 3A-3F. Pinion 503 is adapted to cooperate with saidfirst and second gear stretch 504, 505 for making the billhook 100perform the first and second full rotation respectively when said discis rotated for forming the first and the second knot, respectively.Pinion 503 is disposed for meshing engagement with at the first and asecond circumferentially spaced gear stretches 504, 505 on the knotterdisc 501.

The knotter disc 501 is provided with a first recess 550 downstream offirst gear stretch 504 and with a second recess 555 downstream of secondgear stretch 505, when looking into the direction of movement of pinion503 relative to knotter disk 501, see FIG. 3E. It is also possible tohave only the first recess 550 or only the second recess 555. For eachrecess 550, 555 an obstacle 560, 565 is arranged for engaging pinion 503when pinion 503 moves in recess 550, 555. The first recess 550 and thefirst obstacle 560 are configured to rotate pinion 503 over a determinedangle and back in order to move upper lip 101 of billhook 100 away fromlower lip 102 and back after the first full rotation. The second recess555 and the second obstacle 565 are configured to rotate pinion 503 overa determined angle and back in order to move upper lip 101 of billhook100 away from lower lip 102 and back after the second full rotation.

The obstacle 560, 565 may be a spring mounted element fixed to theknotter disc 501. In the illustrated embodiment the first obstacle 560is a spring-mounted arm and the second obstacle 565 is a spring-mountedwheel. More generally, both obstacles may be the same or different.

Both the first recess 555 and the second recess 565 extends along thecircumference of the disc over a first angular distance α1 and a secondangular distance α2 of 10-90 degrees, preferably 20-60 degrees, morepreferably between 30 and 50 degrees.

As best illustrated in FIG. 3E, the first gear stretch 504 has an outergear stretch 504 a arranged on an outwardly protruding portion of theknotter disc 501, and a inner gear stretch 504 b delimited by adownstream and upstream bottom land portion 504 c, 504 d. Similarly, thesecond gear stretch 505 has an outer gear stretch 505 a arranged on anoutwardly protruding portion of the knotter disc 501, and a inner gearstretch 505 b delimited by a downstream and upstream bottom land portion505 c, 505 d. As best illustrated in FIG. 3F, pinion 503 comprises anouter teeth range 503 a configured to cooperate with the outer gearstretch 504 a, 505 a, and an inner teeth range 503 b configured tocooperate with the inner gear stretch 504 b, 505 b. The inner teethrange 503 b is delimited by a contact portion 503 c. Contact portion 503c is configured to rotate in the downstream and upstream bottom landportion 504 c, 504 d; 505 c, 505 d and to slide over a circumferentialedge 501 e of the top surface the knotter disc 501 when pinion 503 isnot engaged with the first or second gear stretch 504, 505, see FIGS. 3Eand 3F. Preferably contact portion 503 c has a substantially flatcontact surface. The first and second recess 550, 555, the inner gearstretches 504 b, 505 b and the downstream and upstream bottom landportions 504 c, 504 d; 505 c, 505 d are positioned on the same circularpath around an axis of the knotter disc 501. Preferably, the angulardistance 131 between the first recess 550 and the downstream bottom landportion 504 d is smaller than 30 degrees, more preferably smaller than20 degrees. Similarly, the angular distance 132 between the first recess555 and the downstream bottom land portion 505 d is smaller than 30degrees, more preferably smaller than 20 degrees. The first recess 555is curved and, seen in a downstream direction, slopes first graduallydownwardly and next gradually upwardly. Similarly, the second recess 565is curved and, seen in a downstream direction, slopes first graduallydownwardly and next gradually upwardly.

The first obstacle 560 is configured to engage the outer teeth range 503b of the pinion 503 whilst the pinion passes in the first recess 550.Similarly, the second obstacle 565 is configured to engage the outerteeth range 503 b of the pinion 503 whilst the pinion passes in thesecond recess 555.

Pinion 503 performs a first full rotation whilst passing over the firstgear stretch 504: during this rotation one outer end of contact portion503 c rotates in upstream land bottom portion 504 c, and the other endof contact portion 503 c rotates in downstream land bottom portion 504d. Next, when passing in first recess 550 pinion 503 is rotated over asmall angle when entering the first recess 550, and rotated back overthe same small angle when leaving the first recess 550. Then pinion 503performs a second full rotation whilst passing over the second gearstretch 505: during this rotation one outer end of contact portion 503 crotates in upstream land bottom portion 505 c, and the other end ofcontact portion 503 c rotates in downstream land bottom portion 505 d.Next, when passing in second recess 555 pinion 503 is rotated over asmall angle when entering the second recess 565, and rotated back overthe same small angle when leaving the second recess 565.

As best illustrated in FIG. 3C, the swing arm 400 has an arm portion 401and a lower end portion 402 and is arranged for moving the lower endportion 402 below the billhook 100, between a backward position and aforward position. The lower end portion 402 comprises a heel portion 410connected to the arm portion 401, a front portion 411, and a sideportion 412. The side portion 412 extends between the billhook 100 andthe twine disc 201 and forms the connection between an end of the heelportion 410 with an opposite end of the front portion 411. The sideportion 412 is provided with a knife blade 403 for cutting twinesbetween the billhook and the twine receiver whilst moving from thebackward position to the forward position. An open area 413 is formedbetween the heel portion 410 and the front portion 412. The open area413 is dimensioned and shaped for being accessible by the twinedelivering system (needle 11 and tucker arm, see further) so that twinescan be delivered through said open area 413 on the billhook 100. Inother words, the lower end portion 402 of the swing arm 400 is shaped insuch a way that there is an opening at a side facing away from the twinedisc 201, said opening being located underneath the billhook 100 in aknotter position of the swing arm 400. The front portion 411 is providedwith a stripping part 404 having an upper surface with a shape that iscomplementary to a shape of a lower surface of the billhook 100, seealso FIGS. 6A and 6B, so that a formed knot can be stripped from thebillhook 100 whilst moving the swing arm from the backward position tothe forward position. In other words the knife blade 403 will severe thetwines 64 a and 66 a in response to a swinging movement of the arm 400which also serves to bring the stripping part 404 in engagement with aknot formed on the billhook 100 for stripping such knot off of thebillhook 100. Further, the front portion 411 has a curved guidance part405 oriented in the direction of the heel part 410. The curved guidancepart 405 is shaped, dimensioned and arranged for guiding the twinestowards the side part 412 during stripping of a formed knot, and more inparticular towards the inner angle formed by the front part 411 and theside part 412. The heel portion 411 has a curved guidance part 406oriented in the direction of the front part 410. The curved guidancepart 406 is arranged for guiding the twines across the billhook duringdelivery and during knotting. There may be provided an additional guidefinger (not shown) to guide the twines before/during/after knotting, asin prior art solutions. Such a twine finger may be configured forguiding at least the needle twine, wherein the twine finger beingmounted moveably below the billhook 100 and the swing arm 400. Drivemeans for the twine finger may then be configured to move the twinefinger at least a first time during the first knot forming cycle and asecond time during the second knot forming cycle. However, in view ofthe guidance parts 405 and 406, the additional guide finger is notrequired.

Driving power is transmitted to the discs of the twine disc 201 througha twine disc pinion 602, a worm gear drive 603 and a bevel gear 604 inposition for sequential meshing engagement with a pair ofcircumferentially spaced gear sections 605, 606 on the knotter disc 501.

Power to swing the arm 400 about the pivot bolt 420 is obtained througha cam follower 430 at the upper end of the arm 400 beyond the pivot bolt420, which is disposed within a cam track 440 on the knotter disc 501. Apair of circumferentially spaced cam shoulders 442 and 444 in the track440 is positioned to sequentially engage the follower 430 to operate thelatter. Cam follower 430 is connected with the swing arm 400. Cam track440 may be provided in disc 501 or in a member mounted for rotatingsynchronously with disc 501, and is adapted for moving the swing arm 400a first time and a second time during the first and the second knotforming cycle, respectively.

A shaft 30 extends parallel with the shaft 502 to a point substantiallyin fore-and-aft alignment with the billhook 100, see FIG. 2. At thatlocation, the shaft 30 fixedly carries a rearward extending tucker arm31. The tucker arm 31 carries a roller 33 at its rearmost end aroundwhich the strand 64 a is entrained. A length of the strand 64 a is alsolooped upwardly around a slacker arm 34 disposed above the tucker arm31. The strand 64 a may be further clamped between a pair of opposedplates (not shown) of a tensioning unit.

In FIG. 2, the needle 11 is still in its home position. At this point inthe bale forming operation, the bale has reached its desired length andit is time to complete the loop around the bale and make the second knotin the loop. It is remarked that at this specific instance, the strand64 a stretches along the top of the bale directly beneath the swing arm400 but, at least for all effective purposes, is out of contact with theknotter 10. The swing arm 400 moves backward, and the needle 11 swingsupwardly toward the knotter 10. It carries with it the strand 66 a asthe latter is paid out by source 74. Note that because the strand 66 ais threaded through the eyelet 21 of needle 11, a length of that strandon the twine source side of the needle 11 is also carried upwardlytoward the knotter 10, such extra length being hereinafter denoted 66 b.As the needle 11 approaches the knotter 10, the tucker arm 31 is alsomoved upward, see FIGS. 6A and 6B. The tucker arm 31 rocks upwardly in acounter-clockwise direction to provide the slack necessary in the strand64 a to accommodate the needle movement. The tip of the needle 11, andmore particularly, the roller 25, snares the strand 64 a as illustratedin FIG. 6C and presents twines 64 a and 66 a in unison to the knotter10.

While the twines 64 a and 66 a are being delivered across the billhook100 to the twine disc 201, the swing arm 400 is in a position to guidethe twines so as to ensure that the twines 64 a and 66 a are both inproper position across the billhook 100, see FIG. 6D. Next, as shown inFIG. 6E, the billhook is opened to ensure that the twines 64 a, 66 a areproperly positioned over the billhook 100, at an end portion of theupper lip 101 near the pivot point with the lower lip 102. Further theguide part 406 of the heel portion 411 may help in ensuring that thetwines 64 a, 66 a are properly placed across an upper lip 101 of thebillhook 100.

In presenting the twines 64 a and 66 a, the needle 11 drapes the twinesacross the billhook 100, optionally with the help of the guidance part406, and thence into awaiting notches 211 of the twine disc 201,whereupon rotation of co-operating discs in the latter, in combinationwith a pressing twine holder 202, serve to firmly grip the twines 64 a,66 a and prevent their escape as the billhook 100 begins its rotation,see FIGS. 6D, 6E, 6F and 6G. At that time the swing arm 400 moves alittle backward (arrow B), moving the front portion 410 away from thebillhook 100, to provide additional space for the rotation of thebillhook.

Typically, the twine disc 201 rotates a quarter of a turn and clamps thetwines 64 a and 66 a firmly together in the first notch 211. Now theneedle 11 can move downward. During the down travel of the needle 11 thetwo twines on the back of the needles are placed in the next notch 212of the twine disc for the second knot, see FIGS. 6F and 6G. While theneedle 11 goes down, the billhook 100 continues to rotate to form thefirst knot. During this further rotation of the billhook 100, thebillhook 100 opens again, see FIG. 6G, such that the twines from firstnotch 211 can be positioned between the upper lip 101 and the lower lip102. The swing arm 400 swings forward (arrow F in FIG. 6H) to cut thetwines under the twine disc with the knife blade 403 and sweeps the knotfrom the billhook 100 with the help of the stripping part 404.

The foregoing described movement on the part of the billhook 100 and thetwine disc 201 are brought about by operable inter-engagement of thegear stretch 504 and gear section 605 on the knotter disc 501 with theirrespective gears 503 and 604 on the billhook 100 and the twine disc 201.Such driving inter-engagement continues until a knot has been formed onthe billhook 100, by which time the needle 11 has begun to withdraw. Atthis point, the cam shoulder 442 of the knotter disc 501 comes intoengagement with the roller 430 of the arm 400 so as to swing the bottomof the latter, and hence the knife 403, across that portion of thetwines between the billhook 100 and the twine disc 201, thereby severingthe same. At the moment of cutting, the twines 64 a and 66 a extend fromin between the lips 101 and 102 towards the twine disc 201, see FIG. 6H.To complete the knot formation, the stripping part 404 engages thetwines 64 a and 66 a which are retained in a twisted manner around thebillhook 100. In so doing, the strand parts lying on top of the upperlip 101 are pulled over the strand parts lying in between the upper andlower lips 101 and 102, thereby forming the first knot. Next, due to thepresence of first recess 550 and first obstacle 560, the billhook 100 isbriefly opened again after the first full rotation of the billhook 100,see FIGS. 6I and 6J. This will allow the first knot to be a loop knot 70a and will facilitate the releasing of the first knot from the billhook100. Besides completing the knot, further motion of the arm 400 alsohelps to strip the finished knot completely from the billhook 100 and todrop the completed loop on the bale as illustrated in FIG. 6J.

When the knot is dropped by the knotter 10, the strand 66 b of needletwine from source 74, as well as strand 64 b of tucker twine from source72 is still retained in the second notch 212 and possibly also in thefirst notch 211 of the twine disc 201. Consequently, as the needle 11continues to retract, the strand 66 b is draped downwardly across thebale chamber 2 thereby pushing the upper lip 101 down because of thepressure of the twines on the upper lip 101, while the tucker arm 31lowers to its normal position. Upon reaching the condition illustratedin FIG. 9B, the strands 64 b and 66 b are in position for initiating thesecond knot forming cycle. In a first angular range of the secondrotation the billhook is briefly opened as illustrated in FIG. 9C, inorder to ensure that the strands 64 a and 66 b are well positioned onthe billhook 100, in a similar manner as described above for the firstknot forming cycle. The swing arm 400, and in particular guidance part406, may help with the proper positioning of the twines 64 b and 66 bacross and in engagement with the billhook 100. Next the billhook 100and the twine disc 201 are operated by their second respective gearstretch 505 and gear section 606 on the knotter disc 501, see FIGS. 9D,9E and 9F, wherein the billhook 100 is opened a second time in a secondangular range of the second rotation, whilst the cam follower 103thereof passes over the second cam 112. Next, due to the presence ofsecond recess 555 and second obstacle 565, the billhook 100 is brieflyopened again after the second full rotation of the billhook 100, seeFIGS. 9G and 9H. This allows the second knot to be a loop knot 70 a andfacilitates the releasing of the second knot from the billhook 100.

Thus, the second knot becomes formed, whereupon the arm 400 is onceagain actuated, but this time by the second cam shoulder 444. Preferablythe twine disc 201 has a protruding ridge 213 positioned after thesecond notch 212, seen in a rotation direction of the disc 201, so thatthe twine holder 202 is moved away from the twine disc 201 when the discis further rotated during the forming of the second knot. Because thefree ends of the strands 64 b and 66 b are considerably longer than thefree ends obtained during the first knot formation, upon finalizing theknot, the free ends of the strands 64 b and 66 b no longer are pulledcompletely out of the knot, resulting in a so-called loop-knot 68 b, asbest seen in FIGS. 9F-9H and in FIG. 2. FIG. 9I illustrates the swingarm 400 with the lower end portion in the forward position, afterremoval of the knot. In this position the cam follower 103 of billhook100 is on the first cam 111, with the billhook 100 open.

FIG. 7A illustrates a first example of a possible twine receiver 200comprising a twine disc 201 and a twine holder 202. The twine disc 201comprises a first disc 221 and a second disc 222 fixed on an axis 223.The twine holder comprises a first press plate 231 and a second pressplate 232 intended for being inserted between the first and second disc221, 222. The first press plate is intended for being in operativecontact with the outer side of the first disc 221. The first disc 221 isprovided at its inner and/or outer side with a protruding ridge 213. Inthe embodiment of FIG. 7A the ridge extends at both sides of the firstdisc 221, while in the embodiment of FIG. 7B the ridge extends only atthe outer side of disc 221. In the variant of FIG. 7A, the first disc221 is provided with an opening 224, and the ridge 213 is formed by apiece 213 that is fixed through the opening 224 on the second disc 222.The skilled person will understand that other shapes are possible andthat it may be possible to provide more or less notches in the twinedisc. However, providing the twine disc with only two notches 211, 212spaced along the circumference at an angle which approximately 90degrees, as in the embodiment of FIG. 7A, is advantageous because thiswill allow the notches to be located at a lower part of the twine discs201 when the knotter is in a non-active state. This will avoid that dirtcan accumulate in the notches in the non-operative state of the knotter.

According to an alternative variant the pressure exerted by the leafspring 220 could be regulated using a setting means adapted to decreasethis pressure at the end of the second rotation of the billhook 100.According to yet another possibility the twine holder 202 could bepushed away against the force of the leaf spring 220 during theformation of the second knot. The skilled person understands that thisregulating of the pressure/pushing away of the twine holder can bereached using any suitable mechanical or hydraulic transfer. Also,instead of providing the spring means 220, there could be provided adifferent actuator for biasing the twine holder 202. Finally the skilledperson understands that an adaption of shape of the notches 211, 212 andthe use of a protruding ridge 213 may be combined.

As illustrated in FIG. 3A-3D, there may be provided a supplementary gearsection 606′ providing a prolonged operation of the twine disc 201, sothat the twine disc rotates over approximately 270 degrees during thesecond knot forming cycle. This prolonged rotation in combination withthe protruding ridge 213 will result in the twines 64 b and 66 b beingno longer retained between the twine disc 201 and the twine holder 202,causing a further slipping of the twines during the forming of thesecond knot. Indeed, even though the knife blade 403 is very sharp, itwill not be able to cut the twines because instead of holding thetwines, the twine disc 201 is releasing them on account of the continuedrotation of the twine disc 201 and the low pressure of the twine holder202 on the twines, while the arm 400 continues moving and stripping ofthe almost completed knot from the billhook 100, thus pulling the twinesout of the twine disc 201. The skilled person understands that thesupplementary gear section 606 is not necessary, and that a similareffect can be reached when the tensioning force of the leaf spring 220to the twine holder 202 is sufficiently decreased.

This second knot is the start of a new bight for the next bale. Suchbight is in position to receive new material that is packed into thebale chamber by the plunger, and the bight grows in length as additionallengths of the twines 64 b and 66 b are simultaneously pulled from theirsources 72 and 74. Finally, when the bale has reached its desired size,the sequence returns to its starting point, whereupon the bight isclosed by operation of the needle 11 to complete the loop around thebale and form the other knot.

In yet another embodiment the cam surface may have only the second cam112 as in prior art solutions and the billhook 100 itself may bemodified to cause the opening of the billhook in the first angular rangeas defined above. For example, as illustrated in FIG. 8 the upper lip101 of billhook may be made heavier at the lower side of downwardlyprotruding end part 104. This additional material can be chosen suchthat the upper lip 101 opens in the first angular range. More inparticular the upper lip 101 may be provided with a hook-like end part104 protruding in the direction of the lower lip. The hook-like end part104 has an inner face 104′ making an obtuse angle α with a lower face101′ of an elongate portion of the upper lip 101. By increasing theangle α the billhook can be more easily opened by a strand. When such anembodiment is used an appropriate compromise has to be found between theshape of the upper lip 101, and in particular of the hook-like end part104, and the tension in strands.

While the principles of the invention have been set out above inconnection with specific embodiments, it is to be understood that thisdescription is merely made by way of example and not as a limitation ofthe scope of protection, which is determined by the appended claims.

The invention claimed is:
 1. A knotter system for performing a knottercycle of a baler, the knotter cycle having at least a first knot formingcycle and a second knot forming cycle, the knotter system comprising: aneedle configured for delivering a needle twine; a tucker arm configuredfor delivering a tucker twine; a billhook assembly comprising a billhookwith a lower lip and an upper lip mounted pivotally with respect tolower lip, the billhook being mounted rotatably around a rotational axisand being arranged for receiving the needle twine and the tucker twine;and a driver adapted to make the billhook perform at least a first fullrotation around its rotational axis during the first knot forming cycleand a second full rotation around its rotational axis during the secondknot forming cycle, wherein the driver comprises a pinion and at least afirst gear stretch and a second gear stretch provided along acircumference of a disc, the pinion being adapted to cooperate with thefirst and second gear stretches for making the billhook perform thefirst and second full rotations respectively when the disc is rotatedfor forming the first knot and the second knot, respectively, whereinthe disc comprises a recess downstream of at least one of the first gearstretch and the second gear stretch, wherein an obstacle is arranged forengaging the pinion when moving in the recess, and wherein the recessand the obstacle are configured to rotate the pinion over a determinedangle and back in order to move the upper lip of the billhook away fromthe lower lip and back after at least one of the first full rotation andthe second full rotation.
 2. The knotter system of claim 1, wherein theobstacle is a spring mounted element fixed to the disc.
 3. The knottersystem of claim 1, wherein the recess extends along the circumference ofthe disc over an angular distance of 10 to 90 degrees.
 4. The knottersystem of claim 1, wherein the obstacle is any one of the following: aspring-mounted arm, a spring mounted wheel.
 5. The knotter system ofclaim 1, wherein at least one of the first gear stretch and the secondgear stretch has an outer gear stretch arranged on an outwardlyprotruding portion of the disc, and an inner gear stretch delimited by adownstream bottom land portion and an upstream bottom land portion; andwherein the pinion comprises an outer teeth range configured tocooperate with the outer gear stretch, and an inner teeth rangeconfigured to cooperate with the inner gear stretch, the inner teethrange being delimited by a contact portion configured to rotate in thedownstream and upstream bottom land portions and to slide over the discwhen the pinion is not engaged with the first gear stretch or the secondgear stretch.
 6. The knotter system of claim 5, wherein the recess isconfigured to receive the contact portion and to cause the contactportion to rotate over the determined angle and back, wherein thecontact portion has a curved contact surface.
 7. The knotter system ofclaim 5, wherein the recess, the inner gear stretch and the downstreamand upstream bottom land portions are positioned on the same circularpath around an axis of the disc.
 8. The knotter system of claim 5,wherein an angular distance between the recess and the downstream bottomland portion is smaller than 30 degrees.
 9. The knotter system of claim5, wherein the obstacle is configured to engage the outer teeth range ofthe pinion.
 10. The knotter system of claim 5, wherein the recess, seenin a downstream direction, slopes first gradually downwardly and nextgradually upwardly.
 11. The knotter system of claim 1, wherein thebillhook assembly is configured to position the upper lip away from thelower lip in a first angular range and to position the upper lip awayfrom the lower lip in a second angular range of at least one of thefirst full rotation and the second full rotation, wherein the firstangular range is located within a range between 0° and 160°, and thesecond angular range is located within a range between 160° and 360°.12. The knotter system of claim 11, wherein the billhook assembly isconfigured to move the upper lip away from the lower lip and back afirst time in the first angular range and to move the upper lip awayfrom the lower lip a second time in the second angular range.
 13. Theknotter system of claim 11, wherein the billhook assembly comprises acam surface, and wherein the billhook is provided with a cam follower incontact with the cam surface-, the cam surface being configured formoving the upper lip away from the lower lip.
 14. The knotter system ofclaim 13, wherein the cam surface is provided with a first and a secondcam configured for pushing the upper lip away from the lower lip, in thefirst angular range and in the second angular range, respectively,during the first full rotation and during the second full rotation. 15.The knotter system of claim 1, further comprising: a twine receiverconfigured for holding the needle twine and the tucker twine; and aswing arm adapted for cutting twines between the billhook and the twinereceiver, the driver is further configured to move the swing arm a firsttime from a rest position to an extended position and back during thefirst knot forming cycle and a second time during the second knotforming cycle.
 16. The knotter system of claim 15, wherein the swing armis configured for sweeping a formed knot from the billhook during thefirst knot forming cycle and during the second knot forming cycle,respectively.
 17. The knotter system claim 15, wherein the twinereceiver is adapted to let the twines slip during the second knotforming cycle so that cutting of the needle and the tucker twine isavoided when forming the second knot.
 18. The knotter system of claim15, wherein the driver comprises a cam track and a cam follower, the camfollower being connected with the swing arm, and the cam track beingprovided in the disc or in a member mounted for rotating synchronouslywith the disc, and being adapted for moving the swing arm a first timeand a second time during the first knot forming cycle and the secondknot forming cycle, respectively.
 19. A baler comprising a plurality ofknotter systems, each of the plurality of knotter systems for performinga knotter cycle of the baler, the knotter cycle having at least a firstknot forming cycle and a second knot forming cycle, each of theplurality of knotter systems comprising: a needle configured fordelivering a needle twine; a tucker arm configured for delivering atucker twine; a billhook assembly comprising a billhook with a lower lipand an upper lip mounted pivotally with respect to lower lip, thebillhook being mounted rotatably around a rotational axis and beingarranged for receiving the needle twine and the tucker twine; and adriver adapted to make the billhook perform at least a first fullrotation around its rotational axis during the first knot forming cycleand a second full rotation around its rotational axis during the secondknot forming cycle, wherein the driver comprises a pinion and at least afirst gear stretch and a second gear stretch provided along acircumference of a disc, the pinion being adapted to cooperate with thefirst and second gear stretches for making the billhook perform thefirst and second full rotations respectively when the disc is rotatedfor forming the first knot and the second knot, respectively, whereinthe disc comprises a recess downstream of at least one of the first gearstretch and the second gear stretch, wherein an obstacle is arranged forengaging the pinion when moving in the recess, and wherein the recessand the obstacle are configured to rotate the pinion over a determinedangle and back in order to move the upper lip of the billhook away fromthe lower lip and back after at least one of the first full rotation andthe second full rotation.